A growing number of companies are developing vehicles that use electric motors as the means for propelling the vehicles. And because electric motors can be designed to be very compact and efficient, especially as compared to combustion engines, they are also being used as in-wheel or hub motors, with an electric motor mounted in or very close to each of the wheels of the vehicle. Some of the newer, more innovative designs for vehicle drive systems are not only capable of rotating the wheel but are also capable of moving the wheel in directions that are transverse to the rotational axis. That is, they are capable of producing movement with two degrees of freedom, namely, rotation to propel the vehicle along the road and translation to provide an active suspension for the vehicle.
One example of such a system is described in U.S. Pat. No. 8,519,575 and is based on the use of Lorentz-force, linear actuators. To achieve the two degrees of freedom, it uses two opposed linear actuators and a linear-to-rotary converter that is made up of an arrangement of cam followers interfacing with a cam assembly that supports a wheel rim. The linear actuators are opposed to each other in that they lie on opposite sides of the rotational axis of the wheel. When the two opposed linear actuators are operated to move the cam followers towards each other or away from each other in synchronization, the linear-to-rotary converter converts that movement to pure rotation of the wheel. When the two linear actuators are operated to move the cam followers in the same direction (i.e., one moving towards the rotational axis and the other away), this causes the cam assembly and the wheel to which it is attached to translate in a direction that is transverse to the axis of rotation of the wheel.